I. A. Yakunin

Magnetic field monitoring of the very slowly rotating CP star HD 965

With the 6-m telescope we performed the magnetic field Be measurements for the chemically peculiar star HD 965. During 2000–2015 we obtained over 30 spectra with a Zeeman circular polarization analyzer. The longitudinal field reaches +600 G at the positive extremum and goes below −1300 G at the negative one. The magnetic monitoring of the star shows that the period of Be variability, i.e., the rotation period, exceeds 15 years. Thus, HD 965 belongs to the five slowest rotators among magnetic stars.

Magnetic Field Measurement of the Star HD 35298

Based on the spectropolarimetric data obtained at the 6-m telescope, a study of the magnetic field and physical parameters of the magnetic He-weak star HD 35298 was performed. A comparison of the results of magnetic field measurements by various methods has been carried out. The star’s magnetic field varies in the range from −3 to +3 kG. The field geometry is explained in terms of the oblique rotator model. The obtained magnetic field variation curve can be described by a central dipole with the dipole axis inclined to the axis of rotation by β = 60°, and the magnetic field strength at the pole of Bp = 11.5 kG. The data on the variability of spectral lines of some metals are presented, allowing to make an assumption that the stellar surface is heavily spotted.

Chemically peculiar stars in the orion OB1 association. I. occurrence frequency, spatial distribution, and kinematics

A total of 85 CP stars of various types are identified among 814 members of the OriOB1 association. The fraction of CP stars decreases with age for different cluster subgroups: from 15.1% in the youngest subgroup (b) to 7.7% in the oldest one (a). Individual comments are provided for each of the 85 stars, where we analyze the physical parameters and distance of the objects. All the 23 Am stars identified as a result of this study are found to have heliocentric distances between 100 and 300 pc and appear not to be members of the OrionOB1 association, but foreground objects. We identified 59 Bp stars, which account for 13.4% of the total number of B-type stars in the association. The fraction of peculiar B-type stars in the OriOB1 association is found to be twice higher than that of peculiar A-type stars. The same is true for field stars. The association contains 22 magnetic stars, out of which 21 are Bp stars and only one is an Ap star. Seventeen of these stars are objects with anomalous helium lines. Magnetic stars show a well-defined tendency to concentrate in the central region of the association (in Orion’s Belt), which contains most of these objects. No significant differences are found between the field strengths in the B-type stars of the association and Bp-type field stars, although there is a noticeable trend for He-rich stars to have stronger fields compared to He-weak stars. We identified 17 binaries, which make up 20% of the total number of peculiar stars studied, which is the standard ratio for CP stars. Except for one HgMn star (HD35548), the radial velocities and proper motions of our identified objects are consistent with the corresponding parameters of normal B-type stars.

On discovery of strong magnetic field in the binary system HD34736

We present the results of a study of the star HD34736. The spectropolarimetric observations carried out at the 6-m telescope showed the presence of a strong variable longitudinal magnetic field, exceeding −4500 G. The analysis of the Hipparcos photometry gives a set of possible periods of the brightness variability of the star, of which

Magnetic field of CP stars in the Ori OB1 association. II. HD36540, HD36668, HD36916, HD37058

0_.^d 3603

Spots and activity cycles of the star FKCom—2013–2015 data analysis

is preferred. The variable radial velocity of spectral lines of the star and some signatures of lines of at least one other component show that HD34736 is a binary short-period system. Modeling of the spectra allowed us to estimate the effective temperature Teff of the stars (13 700 and 11 500 K) and their projected rotational velocities υ sin i (73 and ≥ 90 km s−1). The analysis of all the available information about the star allows us to hypothesize that the object of study is a close, possibly interacting binary system.

Results of Magnetic-Field Measurements with the 6-m Telescope. V. Observations in 2011

We present the results of magnetic field measurements of four chemically peculiar (CP) stars, the members of the Orion stellar association OB1. Observations were carried out with the circular polarization analyzer at the Main Stellar Spectrograph of the 6-m telescope. All the studied stars refer to the subtype of Bp stars with weak helium lines. Canadian astronomer E. F. Borra detected a magnetic field in three of them (HD35456, HD36313, and HD36526) from the Balmer line magnetometer observations. HD35881 was observed for the first time for the purpose to search for a magnetic field. We obtained the following results: HD35456 is a magnetic star with longitudinal field variation range from +300 to +650 G and a period of 4.9506 days; HD35881 is possible a new magnetic star, the longitudinal component of which varies from−1 to +1 kGwith a period of 0.6998 days, however, a small number of lines broadened by rotation does not allow us to conduct measurements more accurately; HD36313 is a binary star with the components similar in brightness, the primary component is a magnetic star with broad lines, the magnetic field of the secondary component (the star with narrow lines) was not detected. Measurements in the Hβ hydrogen line showed the variations of the longitudinal component from −1.5 to +2 kG with a period of 1.17862 days; a strong longitudinal field was detected in HD36526 (from 0 to +3000 G) varying with a rotation period of the star of 3.081 days. In all the cases, we observe considerable discrepancies with the data on magnetic fields of these objects obtained earlier.

Magnetic stars with wide depressions in the continuum. 2. The silicon star with a complex field structure HD 27404

We present the results of magnetic field measurements of four chemically peculiar (CP) stars with helium abundance anomalies which are the members of the Orion stellar association OB1. The stars under study were classified as magnetic by other authors earlier. The present paper contains the results of the extensive study of the stars. Magnetic field measurements allowed us to conclude that HD36540 has a weak field and the longitudinal component Be does not exceed 500 G. The longitudinal field of HD36668 varies with the period P = 2.d 11884 and the amplitude from −2 to +2 kG. The magnetic field of HD36916 has mainly negative polarity and varies within the range from 0 to −1 kG with the period P = 1.d 565238. HD37058 is a magnetic star, the longitudinal field of which varies from −1.2 to +0.8 kG with the period P = 14.d 659. The Be field variability pattern for the stars HD36916 and HD37058 is of a simple harmonic type. The longitudinal field of HD36668 is best described with two combined harmonic functions (“a doublewave”). The variability period of HD36540 is still undetermined. For all the stars from this paper, we measured radial velocities Vr, axial rotation rates ve sin i, and determined basic parameters of atmospheres (effective temperatures Teff and gravity acceleration log g). We also estimated masses M, luminosities L, and radii R of the stars.